1. Field of the Invention
The present invention relates to an apparatus and method for a mobile communication system, and more particularly to an apparatus and method for controlling the duplication structure of a base station transceiver subsystem in the mobile communication system having a sector structure.
2. Description of the Related Art
FIG. 1 is a block diagram illustrating an internal structure of a conventional base station transceiver subsystem having three sectors and two frequency assignments.
In general, a Base station Transceiver Subsystem (BTS) in a mobile communication system using a general Code Division Multiple Access (CDMA) scheme has a sectoral cell structure. Sectoral cell structure refers to a structure in which a cell covered by the BTS is divided into and managed as a predetermined number of sectors. Here, the BTS has a cell including the three sectors of α, β, and γ. The number of frequency assignments (FAs) used by the BTS may be variable according to the circumstances. Further, the BTS employs power dividers and power combiners. The power divider/power combiner may have different constructions according to configurations and capacity of the corresponding BTS, such as FA structure and sector structure of the BTS.
Referring to FIG. 1, the BTS has three sectors and two FAs. Therefore, each of the three sectors has a reception structure for each of the two FAs. That is, for the α sector, the BTS includes an antenna 111, a band pass filter 113, and a power divider 115. For the β sector, the BTS includes an antenna 121, a band pass filter 123, and a power divider 125. Also, for the γ sector, the BTS includes an antenna 131, a band pass filter 133, and a power divider 135. In addition, the BTS includes a 6:7 switch 150, a receiving section 160, and a controller 161. The 6:7 switch 150 connects signals outputted from the power dividers 115, 125, and 135 to corresponding receivers in the receiving section 160. The receiving section 160 includes receivers for processing α sector signals, receivers for processing β sector signals, receivers for processing γ sector signals, and a redundancy receiver provided for a case where any of the receivers for processing the α, β, and γ sector signals functions erroneously. The controller 161 controls the operation of the 6:7 switch for connecting the signals from the power dividers 115, 125, and 135 to the corresponding receivers in the receiving section 160 according to the states of the corresponding receivers.
Hereinafter, processes through which signals received through the α, β, and γ sectors are transferred to the corresponding receivers will be described, and a process through which a signal received through the α sector is transferred to corresponding receivers will be first described.
First, when an α sector signal is received through the antenna 111, the antenna 111 outputs the received signal to the band pass filter 113. The band pass filter 113 receives the signal outputted from the antenna 111, filters the received signal in accordance with a predetermined band, and then outputs the filtered signal to the power divider 115. Here, the band pass filter 113 eliminates components of unnecessary bands included in the signal outputted from the antenna 111 through the filtering. The power divider 115 divides the signal outputted from the band pass filter 113 into two half-power signals and outputs the half-power signals to the 6:7 switch 150. Here, the power divider 115 divides the signal outputted from the band pass filter 113 into two half-power signals because the BTS has two FAs. Meanwhile, the 6:7 switch 150 has six input ports and seven output ports. The six input ports are assigned in pairs to each of the power dividers 115, 125, and 135 connected to the three sectors, respectively. In other words, in the 6:7 switch 150, input ports 1 and 2 receive the two signals outputted from the power divider 115 for processing the α sector signal, input ports 3 and 4 receive two signals outputted from the power divider 125 for processing the β sector signal, and input ports 5 and 6 receive two signals outputted from the power divider 135 for processing the γ sector signal. Then, the 6:7 switch 150 transfers the signals, which have been inputted through the input ports 1 and 2, through output ports 11 and 12 to corresponding receivers, that is, a first receiver 117 and a second receiver (not shown) in the receiving section 160.
Second, a process through which a signal received through the β sector is transferred to corresponding receivers will be described below.
When a β sector signal is received through the antenna 121, the antenna 121 outputs the received signal to the band pass filter 123. The band pass filter 123 receives the signal outputted from the antenna 121, filters the received signal in accordance with a predetermined band, and then outputs the filtered signal to the power divider 125. The power divider 125 divides the signal outputted from the band pass filter 123 into two half-power signals and outputs the half-power signals to the 6:7 switch 150. Then, the 6:7 switch 150 receives the signals from the power divider 125 through the input ports 3 and 4 and transfers the signals through output ports 13 and 14 to corresponding receivers, that is, third receiver (not shown) and fourth receiver (not shown) in the receiving section 160.
Third, a process through which a signal received through the γ sector is transferred to corresponding receivers will be described below.
When a γ sector signal is received through the antenna 131, the antenna 131 outputs the received signal to the band pass filter 133. The band pass filter 133 receives the signal outputted from the antenna 131, filters the received signal in accordance with a predetermined band, and then outputs the filtered signal to the power divider 135. The power divider 135 divides the signal outputted from the band pass filter 133 into two half-power signals and outputs the half-power signals to the 6:7 switch 150. Then, the 6:7 switch 150 receives the signals from the power divider 135 through the input ports 5 and 6 and transfers the signals through output ports 15 and 16 to corresponding receivers, that is, a fifth receiver (not shown) and a sixth receiver 127 in the receiving section 160.
While the signals received through the α, β, and γ sectors in this way are normally demodulated in the corresponding receivers, any receiver from among the receivers described above may function erroneously. When one of the receivers functions erroneously, the redundancy receiver 137 is used instead of the erroneous receiver which cannot perform a normal operation of demodulating a received signal. That is, the connection is switched over from the erroneous receiver to the redundancy receiver 137, so that the redundancy receiver 137 in place of the erroneous receiver can perform the demodulation of the received signal. The controller 161 periodically monitors the states of the receivers. When the controller 161 detects the existence of any erroneous receiver from among the receivers, the controller 161 controls the 6:7 switch 150 to connect the signal, which has been connected to an output port connected to the erroneous receiver, to another output port connected to the redundancy receiver 137, that is, the output port 17.
For example, when the first receiver 117 functions erroneously, the controller 161 detects the error function of the first receiver 117 and controls the 6:7 switch 150 to switch the connection over from the first receiver 117 to the redundancy receiver 137. As the connection is switched over from the first receiver 117 to the redundancy receiver 137 by the controller 161, the signal having been connected to the first receiver 117, which is inputted through the input port 1, is connected to the output port connected to the redundancy receiver 137, that is, the output port 17. As a result, the BTS can always perform exact demodulation of received signals by switching over from the erroneous receiver to the redundancy receiver.
While the above description with reference to FIG. 1 is given of an internal structure, especially a receiver connection structure, of a BTS having three sectors and two FAs, an internal structure of a BTS having four FAs with no sectoral structure will be described hereinafter with reference to FIG. 2.
FIG. 2 schematically is a block diagram illustrating an internal structure of a conventional BTS having four FAs with no sectoral structure.
The BTS may have either a sectoral structure as that described with reference to FIG. 1 or an omni-directional structure having no sector. The BTS shown in FIG. 2 has an omni-directional structure in which the BTS receives signals via a single omni-directional antenna.
Referring to FIG. 2, when a signal is received through an antenna 211, the antenna 211 outputs the received signal to a band pass filter 213. The band pass filter 213 receives the signal outputted from the antenna 211, filters the received signal in accordance with a predetermined band, and then outputs the filtered signal to a power divider 215. In this case, the band pass filter 213 eliminates components of unnecessary bands included in the signal outputted from the antenna 211 through the filtering. The power divider 215 divides the signal outputted from the band pass filter 213 into four quarter-power signals and outputs the four quarter-power signals to a 4:5 switch 217. Here, the power divider 215 divides the signal outputted from the band pass filter 213 into four quarter-power signals because the BTS has four FAs. Meanwhile, the 4:5 switch 217 has four input ports and five output ports. That is to say, the 4:5 switch 217 receives the four signals power-divided in the power divider 215 through the input ports 1 to 4 and connects them to corresponding output ports 11 to 14. In the 4:5 switch 217, a signal inputted through the input port 1 is connected to the output port 11, a signal inputted through the input port 2 is connected to the output port 12, a signal inputted through the input port 3 is connected to the output port 13, and a signal inputted through the input port 4 is connected to the output port 14.
Then, the signal connected to the output port 11 is inputted to the first receiver 221, the signal connected to the output port 12 is inputted to the second receiver 223, the signal connected to the output port 13 is inputted to the third receiver 225, and the signal connected to the output port 14 is inputted to the fourth receiver 227. While the signals received in this way are normally demodulated in the corresponding receivers, any receiver from among the receivers described above may function erroneously. When one of the receivers functions erroneously, the redundancy receiver 229 is used in place of the erroneous receiver which cannot perform a normal operation of demodulating a received signal. That is, the connection is switched over from the erroneous receiver to the redundancy receiver 229, so that the redundancy receiver 229 can perform the demodulation of the received signal on behalf of the erroneous receiver. The controller 219 periodically monitors the states of the receivers. When the controller 219 detects the existence of any erroneous receiver from among the receivers, the controller 219 controls the 4:5 switch 217 to connect the signal, which was connected to an output port connected of the erroneous receiver, to another output port connected to the redundancy receiver 229, that is, the output port 15.
For example, when the first receiver 221 functions erroneously, the controller 219 detects the error function of the first receiver 221 and controls the 4:5 switch 217 to switch the connection over from the first receiver 221 to the redundancy receiver 229. As the connection is switched over from the first receiver 221 to the redundancy receiver 229 by the controller 219, the signal having been connected to the first receiver 221, which is inputted through the input port 1, is connected to the output port 15 connected to the redundancy receiver 229. As a result, the BTS can always perform an exact demodulation of received signals by switching the connection over from the erroneous receiver to the redundancy receiver.
While the above description with reference to FIG. 2 is given of an internal structure, especially a receiver connection structure, of a BTS having four FAs with no sectoral structure, an internal structure of a BTS having three sectors and M number of FAs will be described hereinafter with reference to FIG. 3.
FIG. 3 is a block diagram illustrating an internal structure of a conventional BTS having three sectors and M number of FAs.
In the following description in relation to FIG. 3, description about antennas 311, 321, and 331 and band pass filters 313, 323, and 333 will be omitted because they perform the same functions as those of the antenna 111, 121, and 131 and band pass filters 113, 123, and 133 shown in FIG. 1. Although the power dividers 315, 325, and 335 perform the power-dividing operations in the same manner as the power dividers 115, 125, and 135 in FIG. 1, since the BTS has M number of FAs, each of the power dividers 315, 325, and 335 divides an input signal into M number of equal-power signals each having a 1/M power and outputs the divided signals to an N:(N+1) switch 350. Here, N represents 3M. Then, the N:(N+1) switch 350 receives signals outputted from the power dividers 315, 325, and 335 and connects the signals to corresponding receivers of the receiving section 370, which means the first to Nth receivers 317 to 373. Here, the N:(N+1) switch 350 has N number of input ports, that is, input ports 1 to N, and (N+1) number of output ports, that is, output ports 1(1) to 1(N+1). In the N:(N+1) switch 350, the N number of input ports receive the signals outputted from the power dividers 315, 325, and 335, and the output ports 1(1) to 1(N) from among the (N+1) number of output ports connect the signals inputted through the N number of input ports to the first to Nth receivers 371 to 373. Further, the remaining one output port, namely the output port 1(N+1), is connected to a redundancy receiver 375.
While the signals received in this way are normally demodulated in the corresponding receivers, any receiver from among the receivers described above may function erroneously. When one of the receivers functions erroneously, the redundancy receiver 375 is used in place of the erroneous receiver which cannot perform a normal operation of demodulating a received signal. That is, the connection is switched over from the erroneous receiver to the redundancy receiver 375, so that the redundancy receiver 375 can perform the demodulation of the received signal on behalf of the erroneous receiver. The controller 351 periodically monitors states of the receivers. When the controller 351 detects the existence of any erroneous receiver from among the receivers, the controller 351 controls the N:(N+1) switch 350 to connect the signal, which was connected to an output port of the erroneous receiver, to another output port connected to the redundancy receiver 375.
For example, if the first receiver 371 functions erroneously, the controller 351 detects the error function of the first receiver 371 and controls the N:(N+1) switch 350 to switch the connection over from the first receiver 371 to the redundancy receiver 375. In the N:(N+1) switch 350, as the connection is switched over from the first receiver 371 to the redundancy receiver 375 by the controller 351, the signal that was connected to the first receiver 371, which is inputted through the input port 1, is connected to the output port connected to the redundancy receiver 375, which means the output port N+1. As a result, the BTS can always perform exact demodulation of received signals by switching the connection over from the erroneous receiver to the redundancy receiver.
As apparent from the above description, the switch construction of the BTS is determined by the number of receivers provided at the BTS, which means that the switch construction depends on the number of receivers from which a redundancy receiver must be prepared for erroneous functioning. For example, when the BTS has seven receivers including a redundancy receiver, the BTS needs a 6:7 switch. As the number of receivers for any trouble of which the redundancy receiver must prepare increases, the switch construction becomes correspondingly more complicated. When the number of receivers for any trouble of which the redundancy receiver must prepare is 12, the BTS has 13 receivers including the redundancy receiver, which requires the BTS to be provided with a 12:13 switch. The 12:13 switch should have 25 ports including 12 input ports and 13 output ports. An increase in the number of the ports in the switch increases the size of the switch, thereby causing the switch to occupy a larger space. Further, as the number of the ports increases, supplementary devices for controlling the ports correspondingly increase, thereby increasing the manufacturing cost. Further, it is impossible to know the state of the redundancy receiver before the redundancy receiver is used. Therefore, even after the connection is switched over from a erroneous receiver to an abnormally operating redundancy receiver, it is still impossible to demodulate the signal that was processed by the erroneous receiver, which causes it to be impossible for the BTS to normally operate, thereby deteriorating the quality of service by the BTS.